Update python-slugify requirement from <3.0.0,>=1.2.1 to >=1.2.1,<8.0.0

Updates the requirements on [python-slugify](https://github.com/un33k/python-slugify) to permit the latest version.
- [Release notes](https://github.com/un33k/python-slugify/releases)
- [Changelog](https://github.com/un33k/python-slugify/blob/master/CHANGELOG.md)
- [Commits](https://github.com/un33k/python-slugify/compare/1.2.1...v7.0.0)

---
updated-dependencies:
- dependency-name: python-slugify
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1,7 +1,7 @@
 PyQt5>=5.6.0
 Pillow>=5.2.0
 psutil>=5.0.0
-python-slugify>=1.2.1,<3.0.0
+python-slugify>=1.2.1,<8.0.0
 raven>=6.0.0
 # PyQt5-tools
 mozjpeg-lossless-optimization

setup.py

@@ -94,7 +94,7 @@ setuptools.setup(
         'PyQt5>=5.6.0',
         'Pillow>=5.2.0',
         'psutil>=5.0.0',
-        'python-slugify>=1.2.1,<3.0.0',
+        'python-slugify>=1.2.1,<8.0.0',
         'raven>=6.0.0',
     ],
     classifiers=[],